372 H. A. SPOEHR 



This, however, is purely chemical speculation and so far has 

 aided little in the solution of the problem of photosynthesis, the 

 real course of which is probably far more complicated than has 

 been generally assumed. Not enough work has been done with 

 the chlorophyllous leaf to draw valid conclusions, and this in 

 turn has been due to the fact that the methods of separation 

 and determination have not been sufficiently delicate and ac- 

 curate to permit their application to such sensitive material. 

 Most of the work on the pentoses in plants has been done by 

 means of a method which has recently been found to be quite 

 inadequate and liable to yield erroneous results. That is the 

 method depending upon the formation of furfural from pentoses 

 without a previous separation of the other sugars.^ Also little 

 attempt has been made to distinguish between the soluble mono- 

 molecular pentoses and the condensed pentoses present in the 

 plant as pentosans in the cellulose, slimes and gums. For these 

 reasons the question relative to the origin and function of this 

 group of sugars must be considered as not yet definitely answered 

 in spite of the considerable work which has appeared on the 

 subject. 



Chalmont,-' Tollen,!" Windish and Hasse^^ come to the con- 

 clusion that pentoses are formed from hexoses as first products 

 of oxidation that they are relatively inert and probably are of the 

 nature of waste products. This is based essentially upon their 

 observations that the total pentosan content of seedlings germi- 

 nated and grown in the dark increases with age. The writer 

 made determinations of the total pentoses in seedlings; the re- 

 sults are quite the reverse, however. Wheat seeds were allowed 

 to germinate on glass wool in the dark; at intervals a number of 

 seedlings were removed, dried, ground, hydrolyzed with 1% 



^ Davis, W. A., and G. O. Sawyer, 1. c. 

 Kluyver, J., Biochemische Suikerbepolingen. Leiden. 1914. 

 Cunningham, M. and C. Doree, Biochem. Jour. 8: 438-447, 1914. 

 9 Chalmont, Amer. Chem. Jour. 16: 218, 589, 1894. Ber. d. deutsch. Chem. 

 Ges. 27: 2722, 1894. 



" Tollens, Chem. Zentr. 69: II, 967, 1898. 



" Windish and Hasse, Chem. Zentr. 72: II, 1098, 1901. 



